Low grade papillary urothelial carcinoma

by Jason Wasserman MD PhD FRCPC and Zuzanna Gorski MD
October 2, 2023

What is low grade papillary urothelial carcinoma?

Low grade papillary urothelial carcinoma is a type of cancer that starts in a part of the body called the urinary tract. The urinary tract includes the bladder, ureters, urethra, and kidneys. Most tumours are found in the bladder. This type of cancer is described as “low grade” because the tumour cells look very similar to the normal urothelial cells found in the urinary tract.

Where does low grade papillary urothelial carcinoma start?

Low grade papillary urothelial carcinoma starts from specialized urothelial cells that cover the inside surface of the urinary tract and create a barrier called the urothelium.

What are the symptoms of low grade papillary urothelial carcinoma?

Symptoms of low grade papillary urothelial carcinoma include bloody urine (hematuria), pain when urinating (dysuria), and the need to urinate more frequently.

What causes low grade papillary urothelial carcinoma?

Studies have shown that a wide variety of toxins, medications, and infections are associated with an increased risk of developing papillary urothelial carcinoma. Toxins that can cause this type of cancer include tobacco smoke, opium, benzidine-based dyes, aromatic amines, arsenic, and aristolochic acid produced by Aristolochia plants (which are commonly used in herbal medications). Chronic (long-term) inflammation in the bladder caused by infections such as the Schistosoma haematobium, prolonged indwelling catheter, and some medical treatments including radiation to the pelvis and chemotherapy with chlornaphazine or cyclophosphamide are associated with an increased risk of developing this type of cancer in the bladder.

What does it mean if the tumour is described as non-invasive?

Low grade papillary urothelial carcinoma is described as non-invasive when the tumour cells are only seen in the urothelium. Most tumours are non-invasive. Non-invasive tumours are unable to spread to other parts of the body and are cured by surgery alone.

What does it mean if the tumour is described as invasive?

Low grade papillary urothelial carcinoma is described as invasive if the tumour cells have spread into the layers of tissue below the urothelium. These layers include the lamina propria, muscularis propria, and perivesical soft tissue. Unlike non-invasive tumours, invasive tumours can spread to other parts of the body.

What does depth of invasion mean and why is it important?

The distance that the tumour cells have spread is called the depth of invasion and it can only be determined after the tumour is examined under the microscope. The depth of invasion is very important because tumours that invade deeper into the surrounding tissue are more likely to spread to other parts of the body. The depth of invasion is also used to determine the pathologic tumour stage (pT).

How is this diagnosis made?

The diagnosis is usually made by looking at a urine sample under a microscope. The diagnosis can also be made after a small sample of tissue is removed from the urinary tract during a procedure called a biopsy. After the diagnosis is made, the entire tumour is usually removed in a procedure called transurethral resection (TURBT). For larger tumours that involve the bladder or kidney, part or all of the organ may need to be removed in a procedure called a resection.

Can the tumour grow back after it is removed?

Yes. Approximately 50% of low grade papillary urothelial carcinomas will grow back after being removed. This is called a recurrence. Some tumours can change over time into a more aggressive type of cancer called high grade papillary urothelial carcinoma.

What is the pathologic stage for low grade papillary urothelial carcinoma?

​The pathologic stage for this type of cancer is based on the TNM staging system, an internationally recognized system originally created by the American Joint Committee on Cancer. According to this system, all low grade non-invasive papillary urothelial carcinomas are given a tumour stage of pTa.